Conventional vehicle control involves setting a target operation quantity on the basis of operating characteristics (control map) and controlling the behavior and operation of a vehicle. The operating characteristics (control map) define a correlation between an operation quantity of operation devices (such as accelerator pedal) and an operation quantity (such as acceleration) of the vehicle when an occupant operates the operation devices.
In order to improve an operation feeling of an occupant, a large number of control apparatuses configured to perform vehicle control suited for sensibility of the occupant on the basis of psychophysics have been proposed.
Fechner's law and Stevens' law are known as laws that express the relation between physical quantity and sensory quantity (perception quantity) in the form of functions. Fechner's law states that the sensory quantity is proportional to the logarithm of stimulus intensity, and Stevens' law states that the sensory quantity is proportional to the power of stimulus intensity.
A vehicle control apparatus disclosed in Japanese Unexamined Patent Publication No. 2011-143915 includes an acceleration generation device configured to generate an acceleration to a vehicle and a control device configured to control the acceleration generation device on the basis of an accelerator opening degree corresponding to an accelerator pedal operation by an occupant and a vehicle speed. In the vehicle control apparatus, the relation between the accelerator opening degree and a request acceleration is changed on the basis of a minimum generation acceleration that can be generated by the acceleration generation device while maintaining predetermined characteristics.
A vehicle power steering apparatus disclosed in Japanese Unexamined Patent Publication No. 2015-214295 includes a steering angle sensor, a steering torque sensor, and a control unit configured to control assist power for an electric motor so as to achieve target steering force characteristics defined by a plurality of characteristic elements. In the vehicle power steering apparatus, the control unit includes a sensory quantity setting unit configured to set a plurality of sensory quantities to be estimated to act on an occupant, and a steering force setting unit configured to set target steering force characteristics by converting the plurality of sensory quantities set by the sensory quantity setting unit into physical quantities of a plurality of characteristic elements.
In recent years, vehicles employing a by-wire system have been put into practical use. A vehicle employing a by-wire system includes operation devices to be operated by an occupant, an actuator (reaction motor) for applying an operation reaction force (operation force by the occupant) to the operation devices, and driving devices for operating the vehicle in accordance with an operation quantity of the operation devices.
In the vehicle employing the by-wire system, the operation devices and the driving devices are not mechanically coupled to each other, but an actual vehicle behavioral operation, an operation quantity of operation devices, and an operation force by the occupant are configured as independent elements that are mechanically separated from one another.
In general, vehicle driving involves a transition of driving states in the order of environment recognition by an occupant, situation judgment by the occupant, device operation by the occupant, and response operation by the vehicle.
Recognition, judgement, and operation are elements that are mainly judged by a sensory region (within brain) of the occupant, and the response quantity (responsiveness) of the vehicle is an element that is mainly judged by a physical region (reality).
Specifically, there may be difference between a perception quantity which is perceived by the occupant through visual sensation and somatic sensation and a physical quantity with which the vehicle actually behaves, and there may be difference between a perception quantity which is perceived by the occupant through somatic sensation and a physical quantity with which operation devices actually acts on four limbs and the like.
Therefore, in the situation where the occupant operates operation devices of the vehicle, it is necessary to appropriately apply an operation force that takes sensory characteristics of the occupant into consideration to the occupant on the basis of mechanical characteristics of human four limbs.
The vehicle control apparatus disclosed in Japanese Unexamined Patent Publication No. 2011-143915 generates, on the basis of Fechner's law, an acceleration feeling adapted to sensibility of an occupant with respect to an operation quantity of the accelerator pedal.
The vehicle power steering apparatus disclosed in Japanese Unexamined Patent Publication No. 2015-214295 adjusts, on the basis of Fechner's law, a steering feeling by using an operation feeling of the steering wheel.
The technologies disclosed in Japanese Unexamined Patent Publication Nos. 2011-143915 and 2015-214295, however, have the following problems when a plurality of operation devices are continuously operated in a cooperative manner.
Vehicle driving involves many situations where a plurality of operation devices are continuously operated in a cooperative manner.
For example, vehicle turning travel involves a pedaling operation of a brake pedal and start of steering of a steering wheel during the pedaling operation of the brake pedal in the initial stage of turning and start of pedaling of an accelerator pedal during the steering operation of the steering wheel in the later stage of turning.
Specifically, in a turning initial stage in turning travel of the vehicle, in a state in which a predetermined operation force (pedaling force) in response to the pedaling operation of the brake pedal acts on the leg of the occupant, the occupant starts operation the steering wheel with a low operation force (steering force). Accordingly, the occupant may feel uncomfortable due to the difference in operation force, resulting in increased driving load.
In a turning later stage in turning travel of the vehicle, in a state in which a predetermined operation force (steering force) in response to the steering operation of the steering wheel acts on the arm of the occupant, the occupant starts operating the accelerator pedal with a low operation force (pedaling force). Accordingly, the occupant may feel uncomfortable due to the difference in operation force, resulting in increased driving load.
In other words, in the technologies disclosed in Japanese Unexamined Patent Publication Nos. 2011-143915 and 2015-214295, an operation force of single operation devices can be adapted to the sensibility of the occupant, but the occupant cannot feel a fully comfortable operation feeling when the occupant continuously operates a plurality of operation devices in a cooperative manner.